When driving assistance is provided by displaying a captured image of a vehicle-mounted camera on a monitor screen inside a vehicle, there is known a captured image decision device for deciding display abnormality present in the captured image (see e.g. Patent Document 1).
According to the captured image decision device disclosed in Patent Document 1, color information obtained by a predetermined sampling interval (e.g. a predetermined number of times in one second) set with using a synchronizing signal inputted to a displaying section are added up and if the added-up value in one second is smaller than a first threshold value, the device decides this as display abnormality (black screen state).